Drug delivery devices for setting and dispensing a single or multiple doses of a liquid medicament are as such well-known in the art. Generally, such devices have substantially a similar purpose as that of an ordinary syringe.
Drug delivery devices, in particular pen-type injectors have to meet a number of user-specific requirements. For instance, with patient's suffering chronic diseases, such like diabetes, the patient may be physically infirm and may also have impaired vision. Suitable drug delivery devices especially intended for home medication therefore need to be robust in construction and should be easy to use. Furthermore, manipulation and general handling of the device and its components should be intelligible and easily understandable. Moreover, a dose setting as well as a dose dispensing procedure must be easy to operate and has to be unambiguous.
Typically, such devices comprise a housing adapted to receive a cartridge at least partially filled with the medicament to be dispensed. The devices further comprise a drive mechanism, typically having a displaceable piston rod which is adapted to operably engage with a piston of the cartridge. By means of the drive mechanism and its piston rod, the piston of the cartridge can be displaced in a distal or dispensing direction and may therefore expel a pre-defined amount of the medicament via a piercing assembly which is to be releasably coupled with a distal end section of the housing of the drug delivery device.
Especially with disposable drug delivery devices, in particular with pen-type injectors, the devices are manufactured and assembled in an industrial mass-assembly process. With disposable pen-type injectors, the cartridge filled with the medicament is to be arranged inside the device, which after consumption of the medicament, is to be discarded in its entirety. During assembly of the device, the cartridge being at least partially filled with the medicament is typically assembled in a cartridge holder component, thereby forming a cartridge holder preassembly.
In a similar way, also the drive mechanism of the device to become operably engaged with the cartridge for dispensing a pre-defined dose of the medicament is arranged in a main housing- or body component in order to provide a body sub-assembly. In a final step of assembly, the cartridge holder sub-assembly and the body sub-assembly are mutually assembled and interconnected, e.g. by interconnecting body and cartridge holder. Typically, body and cartridge holder comprise mutually corresponding positive engaging locking members which may provide a non-releasable snap-in interlocking of cartridge holder and body.
Body and cartridge holder may therefore comprise mutually corresponding locking pins or respective protrusions that mate with correspondingly shaped through openings and/or recesses. Since mutually corresponding interlocking members may be comparatively filigree, interconnection of cartridge holder and body may become subject to breakage, for instance when a user unintentionally drops the device. Once, an interlocking member is broken, a stable interconnection of cartridge holder sub-assembly and body sub-assembly might be no longer given and the device in its entirety is of no longer use.
It is therefore achievable to structurally enhance and to improve the interconnection of cartridge holder and body. However, since such devices have to undergo a laborious certification and regulatory processes, usage of e.g. adhesives may have a non-negligible influence on an admission process to release the modified device into the market.